1. Field of the Invention
The present invention relates to a method of producing superconducting wire, and more particularly, to method of producing Nb3Sn superconducting wire.
2. Description of the Related Art
An Nb3Sn superconducting wire, for stability, a structure in which a great number of superconducting filaments having a diameter of a few scores of micrometers are buried in a metal matrix of Cu or the like which has a small resistivity. This structure is called a multifilamentary wire.
According to a conventional method of producing Nb3Sn superconducting wire, first, a plurality of Nb/Cu composites (segments) composed of Cu matrix and Nb multifilament, and Sn cores or Sn alloy cores of the same diameter as that of the segments are prepared. Next, the Sn cores or Sn alloy cores are bundled such that they are surrounded by the segments. Then, they are surrounded by an Nb sheet, and they are inserted in a Cu tube. This is followed by drawing to obtain a wire, and then by heat treatment. In consequence, Sn diffuses in the Cu matrix, Nb3Sn is created around the Nb filaments inside the segments, and an Nb3Sn superconducting wire is obtained as a multifilamentary wire (JP, 09-16731, A).